Present methods of blast cleaning utilize a centrifugal throwing wheel for projecting abrasive particles. The wheel assembly is comprised of a runnerhead with blades or vanes attached and an impeller cage for feeding abrasive particles to the root or heel of the vanes which propel and discharge the particles centrifugally in any desired direction.
The present invention relates to an improved vane configuration which projects the abrasive particles in a narrow pattern, thereby concentrating the blast effect in a manner not available with blast wheels currently on the market. A narrow blast pattern is far more effective on rod and wire product than a relatively wider pattern and also permits selective blast action on larger work pieces where needed, such as in gear peening and for engine block openings.
In the past, efforts have been made to achieve a narrow blast pattern, but these attempts have not been successful. One proposed solution was to provide a channel on the face of the vanes which, while relatively wide at the root of the vanes, narrowed as it approached the tip of the vanes from which the abrasive particles are projected. The tapering side walls of the channel, which forced the abrasive particles toward the center (a narrowed path), of course caused accelerated abrasive wear on the side walls and too frequent replacement of the vanes. Other undesirable effects were noted and will be discussed hereinafter. U.S. Pat. No. 3,287,858, issued Nov. 29, 1966 to R. W. Moore et al shows a vane intended to project a narrow pattern of abrasive particles in accordance with the prior art.